Clamping of parts by adherence on axial thrust support

ABSTRACT

A clamping device, especially for pistons of internal combustion motors, permitting previous indexing and ensuring the handling and maintenance in position of the said pistons during the halffinish and finish machining operations of the skirt and the lands of said pistons. The device comprises a receiving member in frontal support of the head of a workpiece, presenting, centering and indexing members for the piece towards the said receiving member, and members intended to apply the piece against the presenting member by supporting the face of the head of the piece opposite to its face which is frontally supported against the receiving member.

nitewi States atet H 1 Lecaiitei et at.

[ all-.5, 1974 CLAMPING 01F PARTS BY ADHERENCE ON AXIAL THRUST SUPPORT[75] Inventors: Pierre Lecailtel; Bruno Dressler,

both of Billancourt, France [73] Assignees: Regie Nationale Des UsinesRenault,

Billancourt; Automobiles Peugeot, Paris, both of, France 22 Filed: Dec.2, 1971 21 Appl. No.: 204,151

[30] Foreign Application Priority Data Dec. 4, 1970 France 70.43694 Nov.24, 1971 France 71.42070 [52] US. Cl. 279/1 L, 269/50, 269/52, 279/5[51] Int. Cl B23b 5/24 [58] Field of'Search 279/5 1 .l, l L, 1 R; 90/1,90/88; 269/49, 50, 52, 47, 63; 29/559 [56] References Cited UNITEDSTATES PATENTS 3,460,239 8/1969 Nix 29/559 5/1929 Gallimore et al. 279]]R 7/1953 Retz 279/5 X 2,995,989 8/1961 Leboime 269/52 x 2,558,005 6/1951Sciaky 269/52 x 3,200,711 8/1965 Rogg 269/50 X 3,664,227 5 1972 Fischer90 1 ux Primary Examiner-Roy Lake Assistant ExaminerJames F. CoanAttorney, Agent, or FirmStevens, Davis, Miller &

Mosher [5 7] ABSTCT A clamping device, especially for pistons ofinternal combustion motors, permitting previous indexing and ensuringthe handling and maintenance in position of the said pistons duringthehalf-finish and finish machining operations of the skirt and the landsof said pistons.

The device comprises a receiving member in frontal support of the headof a workpiece, presenting, centering and indexing members for the piecetowards the said receiving member, and members intended to apply thepiece against the presenting member by supporting the face of'the headof the piece opposite to its face which is frontally supported againstthe receiving member.

5 Claims, 5 Drawing Figures CLAMIPHNG F PARTS BY ADHERENCE ON AXllALTHRUST SUPPORT The present invention relates to a clamping devicepermitting previous indexing and ensuring the clamping and maintenancein position of engine pistons during semi-finish and finish machiningoperations of the skirts and the lands.

These machining operations give their final form to the profile of thegenerator line and the rectangular sections of the pistons. Until thelast few years, only the machining of the skirt of the piston wasrequired to comply with severe tolerances necessitating the use of acopying machine. During this machining, the gripping of the part waseffected by a claw chuck gripping the first land of the head.

There is now a tendency to make the lands help in the guiding of thepistons and to require from them new qualities. These lands must inparticular have a complex rectangular section, at the same time beingperfectly concentric to the skirt. In consequence, it is now not onlythe skirt of the pistons which must be machined on a copying machine,but the whole of the generator line profile of the piston.

A machining operation of this kind is effected according to theinvention by means of a new clamping device for the workpieces. Thisdevice has the following advantages it leaves the whole generator lineof the piece free for machining, gives good trueing and good centeringof the piece and causes minimum deformation due to clamping whilepermitting previous automatic indexing.

Up to the present time, efforts have been made to obtain such a resultby effecting clamping of the piece by means of a claw chuck, using aboss machined on the compression face of the piston.

This solution provides good trueing and good centering of the piecewithout deformation of the holding means of the piece, but it isexpensive since it requires additional operations, firstly for themachining and then for removing the boss. It becomes very expensive whenthe compression face of the piston is required to be machined.

The clamping device for pistons forming the object of the inventioncomprises essentially a receiving member frontally supporting the headof the piece, members for presenting, centering and indexing the piecetowards the reception member, and devices intended to apply the pieceagainst the presenting member by pressing against the face of the headof the piece opposite to its frontal support face on the receptionmember.

According to a particular form of embodiment of the invention, thereception member is a circular plate carrying three supports cut so asto present, each, four truncated pyramid points. These three supportsare provided in the vicinity of the periphery of the plate and areangularly spaced apart by 120. The plate, which also comprises threeretractable contact fingers serving to support the piston duringindexing, is surrounded by a retractable ring.

The presentation and indexing members comprise essentially anoscillating thrust rod free for rotation about its own axis, elasticallycoupled to a thrust body, and two indexing fingers rigidly fixed to thethrust body and intended to serve as an angular abutment for the bossesof the axis holes of the piston during indexing.

The thrust rod which has especially the purpose of forcing the pistonagainst the plate, is coupled to the thrust body, the displacement ofwhich with respect to the fixed portion of the presenting member isensured by two oppositely acting jacks. The coupling between the rod andthe thrust body is effected in a predetermined manner by two springsacting independently of each other, according to the force required forclamping.

By virtue of this clamping device, the skirt of the piston is entirelyfree for machining. During semi-finish machining, the applied supportingforce is about three times greater than in the case of finish-machining.

In this device, the head of the workpiece, for example the upper face ofa piston, is applied against a reception membercomplete with centeringand indexing members for the piece towards the said centering member,thrust members, in the present case a central supporting finger,applying the piece, by pressure on the face opposite to the head-face,against the receiving member.

In the case of pistons, this arrangement has the advantage on the onehand of completely freeing the outer cylindrical face, which enables itto be machined without repeating the operation, and on the other hand itlimits the supporting and clamping points to the face of the piston headin the absence of any direct mechanical stress on the skirt, whichreduces the risk of deformation due to clamping.

However, since technical development is leading to lighter and lighterpistons and therefore to smaller thicknesses of diaphragm plates on thehead-face and the skirt, it appeared that non-coincidence of thesupports on each side of the head face could result in certain cases inelastic clamping deformations on the skirt. Furthermore, the precisionof centering by rings is conditioned by the accuracy of the diameter ofthe rough piston and their adjustment.

The present invention provides a solution for these 7 problems while atthe same time it simplifies the previous form of construction.

The clamping device according to the invention is characterized by thefact that the receiving member is a circular plate carrying a number ofsupports placed in the vicinity of the periphery of the plate, thepresenting members comprising a thrust rod carrying a rocking levermounted with a swivel joint on the extremity of the thrust rod, the saidrocking lever comprising a number of points which co-operate on theinternal face of the piston head with the said supports of the circularplate.

According to a preferred form of construction of this device, theclamping is modified as follows Centering this is effected by threeretractable elastic fingers moving in synchronism along the generatorlines of a cone I Clamping by internal thrust the thrust is applied atthree points level with the supports of the plate, through theintermediary of three toes mounted on a rocking lever articulated by aswivel joint on the extremity of the thrust rod. There is therefore nodeformation of the piston as a result of its clamping, due to the factof the coincidence of the points of support on each side of thediaphragm plate Indexing The piston is installed pre-indexed. Fineindexing is effected bya member comprising V-shaped portions which issupported on the bosses of the shaft hole and angularly positions thepiston with precision. This indexing is effected during the forwardmovement of the thrust rod Clamping force The previous modificationsrender superfluous the necessity of creating two different conditions offorce for the indexing and finish machining on the one hand, and for therough machining on the other.

The present invention will now be illustrated by means of thedescription which follows of a particular device given with reference tothe accompanying drawings, in which FIG. 1 represents a general view ofthe device in cross-section FIG. 2 represents to a larger scale thecontrol portion of the device between the line A-B of FIG. 1

FIG. 3 represents a view from above of a support of the piston-carrierplate FIG. 4 shows a view of the support shown in FIG. 3, incross-section taken along line IVIV FIG. 5 represents another form ofconstruction of the device, seen in cross-section.

The device according to the invention comprises a piston-carrier plate 1equipped with three supports 2 spaced apart by 120 and each constitutedby four truncated pyramid toes.

Also at the periphery of the plate 1 and at 120 from each other areplaced three contact fingers 3 against which is applied the compressionface of the piston at the moment of its indexing.

The plate 1 is enclosed by a retractable centering ring 4. The forwardand reverse movement of this ring are controlled by a member 5. A spring6 urges the ring 4 in reverse, while ajack 7 causes its forwardmovement. A spring 8 acting on the ring 4 adds its action to that of thethree elastic fingers 3 and of the piston ejector 9. The result is thatthe piston is only in contact with the fingers 3 during the indexing asthe ring 4 is withdrawn during machining, the support is effected at 2.

A thrust rod 11 is mounted on a ball abutment and is for that reasonfree to rotate. Two indexing fingers 12 and 12' are intended to besupported against the bosses of the shaft holes of the pistons. A spring13, provided for indexing and finish machining, is rigidly fixed to theslide 15. A spring 14, provided for semifinish machining, is supportedagainst the circular plate 16 which abuts against the shoulder 21 of thethrust body. The forward or reverse movement of the thrust body 17 iscontrolled by the oppositely-acting jacks l8 and 19.

OPERATION OF THE DEVICE 1. State of the device before presenting apiston 11 Spindle side The fingers 3 are pushed into abutment by theirspring The ejector 9 pushed by its spring 10, is in abutment The ring 4is moved forward by the jack 7, through the intermediary of the spring8. 1-2 Clamping device side The jack 18 being under pressure, its pistonrod is in forward abutment The assembly 17 is at the end of its reartravel, by

means of the jack 19 The cone located to the rear of the rod 11 is incontact with the washer 16.

2. State of the device necessary for indexing (Case of FIGS. 1 and 2)2-1 Spindle side The fingers 3 are still in abutment, pushed by theirspring The piston P, subjected to the action of the clamping device, issupported on these fingers 3 and pushes back the ring 4 together withthe ejector 9.

22 Clamping device side The jack 18 is still under pressure The jack 19has moved the device 17 forward and therefore the piston the jack 18 isunder pressure and serves as an abutment In this case, the rod 11 actson the piston P the cone located at its rear extremity is no longer incontact with the washer l6 The slide 15 coupled axially to the rod isnot in contact with 16 and is only subjected to the action of the spring13.

3. Indexing The spindle is set in rotation at low speed it drives byadherence the piston P, which is stopped angularly against the fingers12 and 12'. The spindle is indexed in turn.

The piston P and the spindle having been separately indexed with respectto the frame of the machine are thus in consequence indexed with respectto each other.

The reverse movement of the sheath 22 ensures the withdrawal of thefingers l2 and 12'.

4. State of the device necessary for half-finish machin- 4-1 Spindleside The ring 4 is withdrawn by means of the jack 7 and the spring 6 Thepiston P is supported at 52 and offers its lateral surface completelyThe fingers 3 and the ejector 9 are pushed back by the piston P.

4-2 Clamping device side The jack 18 having been put off-pressure, itspiston has returned under the thrust of the jack 19 The device 17 thusmoves forward by a few millimeters and the washer 16 comes into contactwith the slide 15 the spring 14 thus applies the necessary clampingforce for semi-finish machin- 5. State of the device necessary forfinish machining.

5-1 Spindle side Identically the same as 4-1.

5-2 Clamping device side The jack 18 being again put under pressure, itsrod pushes back that of the jack 19 and therefore pushes back the device17 which resumes the state 22 The spring 13 applies the clamping forcestrictly necessary for finish machining.

6. Ejection of the piston 6-1 Spindle side condition The fingers 3 andthe ejector 9 are pushed into abutment by their spring. The ejector 9ensures the moving away of the piston The ring 4 remains withdrawn.

6-2 Clamping device side condition The jack 19 remains under pressureThe jack 19 has moved back the device 17.

As can be seen from FIG. 5, the reception members of the piece to beclamped, which in the present case is a piston P, comprise a rod 511which is in cooperation with a jack (not shown) and is surrounded by-amember of revolution 52 associated with a spring 53. The receptionmembers also comprise three centering fingers 54 guided by the mandrel55 and a supporting plate 67 provided with three supporting toes for theupper face of the piston P. The centering fingers 54 are synchronized bya piece 2.

in the piston P are fitted two members 56 and 57, one a supportingmember 56 and the other an indexing member 7, fixed on the extremity ofa thrust rod 58 which is articulated by a swivel joint at the level ofthe bearing 59. The push-rod 58, actuated by a jack (not shown) canrotate in the interior of a casing constituted by the assembly of parts60. The piece 57 is an indexing ring comprising V-shaped parts whichco-operate with the bosses 61 of the axial hole of the piston P. Thispiece 57 is also movable longitudinally through the intermediary of theballs 62, on the rod 58 whichcarries at its extremity a rocking lever 56comprising three toes 63 for supporting the piston P. The hollow parts68 of the two grooves of the push-rod 58 serve as a housing for theballs 62 during the return movement of the thrust rod 58.

The spring 64, mounted on the end rod of the pushrod 58 ensures theclamping force and is supported for reaction against the abutment 66which receives the swivel-joint bearing 59 in the casing 60. The spring65 tends to move apart the rod 51, the piece 52 and the centeringfingers 54.

The operation of the device is as follows I The rod 51 is moved forwardby a jack (not shown) and frees the piece 52 which is pushed by thespring 53 and causes the forward movement of the centering fingers 54guided by the mandrel 55.

The piston P, fitted on the indexing piece 57 and the support piece 56is then presented to the centering fingers 54 by the forward movement ofthe push-rod 58 slightly articulated as a swivel joint at the level ofthe bearing 59. This push-rod 58 is actuated by a jack, not shown,through the assembly of parts 60. The bosses of the axial hole 61 of thepiston are housed in the V- shaped portions of the indexing piece 57.The indexing is then carried out by the pressure of the V-shaped partson the bosses 61 at the moment when the piston head passes into thecentering fingers 54 at the entrance chamfers and is centered inside thesaid fingers.

The centering and indexing are therefore simultaneous. Under the effectof the pressure applied by the push-rod 58, the two balls 62 leave theirrespective housing and the push-rod 58 carrying the rocking lever 66 isapplied by its three toes 63 against the piston. During the retractionof the push-rod 58, the piece 57 is re-set by coming into abutmentagainst a finger, not shown and the balls 62 then enter their respectivestop Vs. The clamping force is provided by the spring 64.

It should be noted that the clamping force is only transmitted by thepush-rod 58, and that, at this moment, no effort is transmitted by thepiece 57.

The fingers 54 are retracted by reversing the jack actuating the rodSll. The spring 65 than pushes back the rod 51, the piece 53 and inconsequence the fingers 54.

All the generator line of the piston P is then free for machining. Thehead of the piston 53 is solely fixed between the three supporting toesof the plate 67 and the three corresponding supporting toes of therocking lever 56 and is not for this reason subjected to any clampingdistortion.

What is claimed is: l. A clamping device for pieces to be machinedadapted for the initial centering and indexing of the work piece such asa piston comprising:

a receiving member adapted for frontly supporting the head of the workpiece;

retractable fingers positioned on said receiving membet for initiallyindexing said work piece;

fixed support members positioned on said receiving member for supportingsaid work piece;

a retractable centering element surrounding said receiving member forinitially centering said work piece and adapted to be retracted awayfrom the work piece during the machining operation;

an oscillating thrust rod free for rotation about its own axis andelastically coupled to a thrust body;

said oscillating thrust rod supporting said work piece on the head ofthe work piece opposite to its front supporting face on said receivingmember; and

indexing fingers rigidly fixed to said thrust body and supported forannular abutment on the bosses of the axial holes of a piston forinitial indexing and adapted for retractable movement along with saidthrust body whereby said indexing fingers do not engage said work pieceduring the machining operation.

2. A clamping device for a piston according to claim 1, wherein saidreceiving member comprises a circular plate and said fixed supportmembers are three members placed in the vicinity of the periphery ofsaid plate and spaced apart by 120.

3. A clamping device for a piston according to claim 1, wherein saidretractable finger members are three members arranged at 120, said fixedsupports are three supports arranged at 120 with each support comprisingfour truncated pyramids and said indexing fingers comprise two fingerson opposite sides of said oscillating thrust rod.

4. A clamping device for a piston according to claim 1, wherein saidoscillating thrust rod is displaced with respect to said receivingmember by two oppositelyacting jacks.

5. A clamping device for a piston according to claim 7 4, wherein saidrod is applied by a predetermined force which act independently.

=l l l=

1. A clamping device for pieces to be machined adapted for the initialcentering and indexing of the work piece such as a piston comprising: areceiving member adapted for frontly supporting the head of the workpiece; retractable fingers positioned on said receiving member forinitially indexing said work piece; fixed support members positioned onsaid receiving member for supporting said work piece; a retractablecentering element surrounding said receiving member for initiallycentering said work piece and adapted to be retracted away from the workpiece during the machining operation; an oscillating thrust rod free forrotation about its own axis and elastically coupled to a thrust body;said oscillating thrust rod supporting said work piece on the head ofthe work piece opposite to its front supporting face on said receivingmember; and indexing fingers rigidly fixed to said thrust body andsupported for annular abutment on the bosses of the axial holes of apiston for initial indexing and adapted for retractable movement alongwith said thrust body whereby said indexing fingers do not engage saidwork piece during the machining operation.
 2. A clamping device for apiston according to claim 1, wherein said receiving member comprises acircular plate and said fixed support members are three members placedin the vicinity of the periphery of said plate and spaced apart by 120*.3. A clamping device for a piston according to claim 1, wherein saidretractable finger members are three members arranged at 120*, saidfixed supports are three supports arranged at 120* with each supportcomprising four truncated pyramids and said indexing fingers comprisetwo fingers on opposite sides of said oscillating thrust rod.
 4. Aclamping device for a piston according to claim 1, wherein saidoscillating thrust rod is displaced with respect to said receivingmember by two oppositely-acting jacks.
 5. A clamping device for a pistonaccording to claim 4, wherein said rod is applied by a predeterminedforce on the bottom of the piston under the action of two springsinterposed between the rod and the thrust body which act independently.